The present invention relates to compositions and articles, and methods of making same, which involve the application of electrical power, more particularly to such compositions, articles and methods wherein one or more material properties are induced electrically.
"Electroset processing" (also referred to as "electrosetting") is the processing of a material by application of a controlled voltage and current through the material during cure. "Programmable" electroset processing is disclosed by Reitz in U.S. Pat. No. 5,518,664, incorporated herein by reference. According to Reitz '664, one or more end-product material properties of a "programmable" electroset composition are "programmably" modified via electroset processing. An "end-product" property is a property which is realized upon the conclusion of the programmable electroset processing, at the stage when the electroset composition has completely cured. Generally, the complete curing of an electroset composition entails the "setting" of the electroset composition so as to achieve some kind of solid state.
To elaborate, Reitz '664 teaches the selective "programmability" of electroset compositions by means of electrical processing during the cure of such compositions; electroset compositions are processed whereby at least one end-product property (e.g., density, compressibility, hardness, buoyancy, smoothness, adhesion or shape) is electrically programmed during curing. As disclosed by Reitz '664, an end-product property is "programmed" in the sense that the end-product property is altered in comparison with what such end-product property would be in the absence of exposure of the composition, during the curing of the composition, to an electric field which is caused by the maintained charging of at least two electrically conductive substrates.
In accordance with Reitz '664, at least two electrodes are utilized with respect to which the programmable electroset composition is interposed. Electrification of the electroset composition is commenced at some point after the composition has been appropriately positioned and while the composition is still fluid and has not fully cured; the electrification of the composition is sustained for a period of time during the curing of the composition Reitz '664 thus suggests continuity of electrification of the composition during cure of the composition; that is, once an electric power supply's electrical power output is intitially applied to the uncured composition, it continues to be applied to the composition until the desired result has been achieved, typically when the composition has substantially cured.
In addition to Reitz '664, the following disclosures, wherein Reitz is sole or joint inventor, pertain to the electroset or electrorheological realm of technology and are incorporated herein by reference: Reitz et al. U.S. Pat. No. 5,232,639; Reitz U.S. Pat. No. 5,213,713; Reitz U.S. Pat. No. 5,194,181; Reitz U.S. Pat. No. 5,190,624; copending patent application Ser. No. 07/810,548 filed Dec. 19, 1991 now abandoned; copending patent application Ser. No. 07/826,207 filed Jan. 22, 1992; and, copending patent application Ser. No. 08/107,047 filed Aug. 17, 1993.
In general, Reitz '664 and other disclosures mentioned hereinabove teach that a significant amount of electrical current, and a nonzero voltage, are applied to (and thus passed through) the electroset composition. Copending patent application Ser. No. 07/826,207 filed Jan. 22, 1992 discloses application to an electrosetting composition of an electric current having an electric current density of at least 0.667 milliamps per square inch. The preferred magnitude of the applied voltage is dependent upon the electroset composition which is being programmed and will usually range from several volts to tens of thousands of volts per centimeter thickness. It is manifest from these disclosures that, in any given instance of electroset processing, the electroset composition must have sufficient electrical conductivity for permitting such voltage and such current to pass therethrough during at least a portion of the duration of the electroset composition's curing.
Reitz '664 teaches the useful and advantageous application of such electrical power to a programmable electroset composition so as to effectuate programming of one or more end-product material properties of the composition. However, electroset processing per Reitz '664 may be less than optimally efficient for certain situations, especially those wherein an electroset composition is intended to be subjected to electroset processing whereby the resultant solidified object has programmed therein a plurality of regions (entire or partial portions) which, locationally, are discrete or distinct.
Dissatisfaction with the electroset processing of Reitz '664 may be heightened if two or more such regions to be programmed have distinctive attributes, i.e., are distinguishible not only in a spatial sense but in a material or qualitative sense, as well. Generally, it would be reasonable to expect, in the light of the teachings of Reitz '664, that electrification of materially/qualitatively distinctive regions would require application of different respective amounts of electrical power in terms of current, or voltage, or both current and voltage.
For instance, take the situation wherein two materially/qualitatively distinctive regions are sought to be programmably processed electrosettably. Each individual region would likely require a different amount of electrical energy (in particular, different voltage and current) to be brought to bear upon it. Pursuant to Reitz '664, a separate power supply would be necessitated for each region, each power supply having it own corresponding set of electrodes. During the curing of the composition, each region would be electrified separately on a continuous basis for some period of time; since each of the respective continuous electrifications would likely be maintained during a substantial portion of the composition's curative window, they would likely be effected at least partially concurrently.
Similarly, three materially/qualitatively distinctive regions would require three separate power supplies, four materially/qualitatively distinctive regions would require four separate power supplies, etc. Power supplies can be costly; the extravagance associated with the supplying of power will be compounded in accordance with the number of power supply units being implemented.
What if, for instance, a practitioner cannot afford or avail himself/herself of more than one power supply for purposes of electrosettably programing two materially/qualitatively distinctive regions? Following the teachings of Reitz '664, the practitioner could position three electrodes (e.g., electrically conductive plates) parallel to and spaced apart from each other, so that there are one "middle" electrode and two "end" electrodes. The programmable electroset composition would be poured into and fill each of the two spaces between the middle electrode and an end electrode.
Hence, pursuant to Reitz '664, there would be two regions, separated by the middle electrode, wherein the programmable electroset composition can be programmed; the two regions would be separately, approximately simultaneously and continuously electrified during the composition's cure, using apparatus inclusive of a common electrode (i.e., the middle electrode). It would in such manner be possible to devise, for a single power source, electrical power system controls which permit the programming of one region at, for example, 3,000 volts and the programming of the other region at, for example, 5,000 volts; however, this may not be feasible or economical.
Moreover, regardless of availability of power supplies, such a tri-electrode approach utilizing one power supply may be dictated by Reitz '664 when two materially/qualitatively distinctive regions are adjacent and so proximate as to prevent placement of two separate pairs of electrodes whereby each electrode pair corresponds to a separate power supply. In such situations, the sharing of the middle electrode would presuppose utilization of a shared power supply. Again, such an arrangement may be problematical.
It is thus seen that the programmable electrosettable processing per Reitz '664 of compositions having a plurality of regions, especially materially/qualitatively distinctive regions, can prove to be an expensive, impractical and/or unwieldy proposition.